David Phillips, senior climatologist at Environment and Climate Change Canada, said Saturday’s storm conditions were different from a system that breeds tornados, with winds all in a straight line, not rotating.
All signs were pointing to thunderstorms in the Ottawa region on Saturday, but even veteran forecasters didn’t foresee the hurricane-strength gusts or the vast area the storm would cover.
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David Phillips, senior climatologist at Environment and Climate Change Canada, was watching conditions build from his home in Orillia.
“On Friday it was looking like it was going to be a tumultuous and active day,” a mix of cool and hot air with the risk of thunderstorms, he said.
“All day (Saturday) I couldn’t get over the fact that the temperature in Ottawa was 30 degrees and the humidex was 38. There has never been a more sultry day in Ottawa this year.
“What is weather? It’s when warm air dukes it out with cold air. That’s essentially where you get violent weather.” And in springtime, “the warm air is never too far from cold air.”
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This storm formed over Southwestern Ontario Saturday morning as cold air blew in from Michigan. It raced east across the countryside, hitting Ottawa in mid-afternoon without much warning. Its arrival was “a very sudden kind of change with lots of strong gusts,” Phillips said.
People were outdoors golfing, boating and preparing for barbecues, and some didn’t have the chance to reach shelter. Three people died in the Ottawa-Gatineau and Renfrew regions and more than 170,000 customers were still without power as of early Sunday afternoon, according to Hydro Ottawa.
Ottawa’s biggest gust reached 120 kilometres per hour Saturday, and Quebec recorded one of 145 km/h, both of which Phillips called “hurricane-force gusts,” though a true hurricane has sustained wind speeds.
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Then around 4 p.m., as the storm blew through, the temperature dropped to 17.5 C and the humidity fell by nearly half, as cooler air pushed in from the west
Phillips said this was different from a storm system that breeds tornados.
“What we see here is a downburst wind,” very high in energy, but travelling in a straight line rather than spinning like a tornado, he said.
One striking aspect was how the storm formed a long line that raced across Ontario from west to east, he said.
“It’s almost like a family of tornados, or a line of microbursts, like soldiers on the front line all moving in the same direction and mowing down everything in its path.”
Such a storm is sometimes called a “derecho,” he said — a storm across a broad area moving for a long distance, with winds all in a straight line, not rotating.
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Phillips later traced the path of the storm and was surprised by its speed: from London around noon, to Toronto at 1 p.m., Kingston by 3 p.m. and Ottawa by 4 p.m., “almost as if it was scripted.
“You couldn’t travel up the (Highway) 401 faster than this system.”
“And it brought the same kinds of weather to all those sites,” all the way to Quebec City, including “toonie-sized hail.
“The damage is very tornado-like.
“It was helped along by that undercutting cold front that pushes that warm, humid air up, and then the rain kind of cools it coming down. It’s almost as if mankind couldn’t produce a more violent kind of system than what we saw.”
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